path: root/lib
diff options
authorFlorian Westphal <fw@strlen.de>2016-08-12 12:03:52 +0200
committerDavid S. Miller <davem@davemloft.net>2016-08-14 21:12:57 -0700
commit4cf0b354d92ee2c642532ee39e330f8f580fd985 (patch)
treebb7716832c6e8174d1c193dcc36c432f07469939 /lib
parent952fcfd08c8109951622579d0ae7b9cd6cafd688 (diff)
rhashtable: avoid large lock-array allocations
Sander reports following splat after netfilter nat bysrc table got converted to rhashtable: swapper/0: page allocation failure: order:3, mode:0x2084020(GFP_ATOMIC|__GFP_COMP) CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.8.0-rc1 [..] [<ffffffff811633ed>] warn_alloc_failed+0xdd/0x140 [<ffffffff811638b1>] __alloc_pages_nodemask+0x3e1/0xcf0 [<ffffffff811a72ed>] alloc_pages_current+0x8d/0x110 [<ffffffff8117cb7f>] kmalloc_order+0x1f/0x70 [<ffffffff811aec19>] __kmalloc+0x129/0x140 [<ffffffff8146d561>] bucket_table_alloc+0xc1/0x1d0 [<ffffffff8146da1d>] rhashtable_insert_rehash+0x5d/0xe0 [<ffffffff819fcfff>] nf_nat_setup_info+0x2ef/0x400 The failure happens when allocating the spinlock array. Even with GFP_KERNEL its unlikely for such a large allocation to succeed. Thomas Graf pointed me at inet_ehash_locks_alloc(), so in addition to adding NOWARN for atomic allocations this also makes the bucket-array sizing more conservative. In commit 095dc8e0c3686 ("tcp: fix/cleanup inet_ehash_locks_alloc()"), Eric Dumazet says: "Budget 2 cache lines per cpu worth of 'spinlocks'". IOW, consider size needed by a single spinlock when determining number of locks per cpu. So with 64 byte per cacheline and 4 byte per spinlock this gives 32 locks per cpu. Resulting size of the lock-array (sizeof(spinlock) == 4): cpus: 1 2 4 8 16 32 64 old: 1k 1k 4k 8k 16k 16k 16k new: 128 256 512 1k 2k 4k 8k 8k allocation should have decent chance of success even with GFP_ATOMIC, and should not fail with GFP_KERNEL. With 72-byte spinlock (LOCKDEP): cpus : 1 2 old: 9k 18k new: ~2k ~4k Reported-by: Sander Eikelenboom <linux@eikelenboom.it> Suggested-by: Thomas Graf <tgraf@suug.ch> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib')
1 files changed, 5 insertions, 2 deletions
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 5d845ffd7982..42acd81f10db 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -30,7 +30,7 @@
#define HASH_MIN_SIZE 4U
static u32 head_hashfn(struct rhashtable *ht,
const struct bucket_table *tbl,
@@ -70,7 +70,7 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
unsigned int nr_pcpus = num_possible_cpus();
- nr_pcpus = min_t(unsigned int, nr_pcpus, 32UL);
+ nr_pcpus = min_t(unsigned int, nr_pcpus, 64UL);
size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
/* Never allocate more than 0.5 locks per bucket */
@@ -83,6 +83,9 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
tbl->locks = vmalloc(size * sizeof(spinlock_t));
+ if (gfp != GFP_KERNEL)
+ gfp |= __GFP_NOWARN | __GFP_NORETRY;
tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
if (!tbl->locks)